Compound ingot.



No. 694,6la. Patentedma. 4, |902.

S. A. CUSGRAVE.

coMPouND man1.

(Application led Jan. 2S, 1900.) No M od el.)

WITNESSES: INVENTOR,

UNITED STATES PATENT OEEiCE.

SYLVESTERA. COSGRAVE, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR, BY MESNEASSIGNMENTS, TO DARWIN S. WOLOOTT, TRUSTEE, OF

SEWIOKLEY, PENNSYLVANIA.

COMPOUND INGOT.

SPECIFICATION forming para ofv Letters Patent No.' 694,618, dated March4, 1902.

' Application tiled January 23, 1900. Serial No. 2,456. (No specimens.)

To a/ZZ whom t mayconcert:

Be it known that I, SYLvEsrER A. Cos- GRAVE, a citizen of the UnitedStates, residing at Pittsburg, inthe county of Allegheny and State ofPennsylvania, have invented or discovered certain new and usefulImprove` ments in Compound Ingots, of which improvements the followingis aspeciication. y' i The invention described Vherein relates tocertain improvements in what is known inthe art as a compound ingot-t'.e., an ingot having varying percentages of carbon in different partsthereof.

It has been characteristic of the compound ingots heretofore producedthat there is a sharp and well-defined line of division between the twogrades or kinds of metal forming the ingot. The line of division is dueto the methods employed in the manufacture of ingots. These methodsywhile differing in small details can be generally classified undertwoheads. One method consists in casting the two grades of metal onopposite sides of a thin metal plate, the integrity of which isdestroyed by the molten bodies of metal. The other method consists incasting one body of metal in a mold having a movable wall, which iswithdrawn as soon as the first body of metal has hardened sufficientlyto preserve its shape and the other 4fbodyof metal cast against theexposed face of the first body. In the practice of this method themolten metal in contact with the movable wall becomes chilled andsolidied, forming a thin metal wall, which is so softened'when thesecond body of metal is cast against it as to permit a welding of thetwo bodies together. It is characteristic of both of these methods thatbetween the two bodies of inetal is interposed a solid metal wall, whichalthough it may be melted and its integrity destroyed will retain itsintegrity for a suflicient length of time to prevent an interchange ofchemical and physical characteristics between the two bodies of metal.It is probable that the thin metal plate or sheet employed in thepractice of the first method introduces a foreign element, whichalthough the sheet is destroyed would prevent the interchange ofcharacteristics, and

in the second method it is probable that the surface exposed on thewithdrawal of the movable wall becomes oxidized or otherwise chemicallychanged, and thereby prevents the desired interchange ofcharacteristics.

While the sharp deiinite separation of the two bodies of metalcharacteristic of compound ingots heretofore produced may be due tocauses other than those stated, such demarcation or stratification ofthe metals al ways occurs. This stratification of the metals is notespecially detrimental when the articles formed therefrom are notsubjected to excessive strains, but is fatal when t-he article,

such as armor-plate formed from such a compound ingot, is subjected toexcessive strains. Under such conditions the two metals separate alongthe plane of stratification.

The invention described herein consists, generally stated, in an ingotformed of two bodies of metal so united that there will be a v gradualchange of characteristics from one body to thev other.

In the accompanying drawings, forming a part of this specitication,Figure 1 is a sectional plan view of a compound ingot wherein Aitscharacteristics gradually or decrementally change from one side to theother, and Fig. 2 is a similar view ofan ingot wherein thecharacteristics change gradually from the outer surfaces to the center.

VThe ingot forming the subject-matter of this case may be produced-inseveral ways as, for example, inthe manner described in Letters PatentNos. 638,908 and 638,961, dated December 12, 1899, or in the mannerforming the subject-matter of application, Serial No. 2,455, tiledJanuary 23, 1900.

The method described in the Letters Patent referred to consists,generally stated, in

casting one body of metal-e. g. ,highcarbon steel-in a mold having amovable wall, removing said wall and causing another body of metal, aslow-carbon steel, tofiow up along the exposed surface of the iirst body,and thereby melting the thin skin formed on the Irst body, and allowingthe two molten bodi" to come together without agitation or turba'nc/eLIn order to protect the sur the first body as againstany elementalchange which would tend to prevent the amalgamation of the adjacentportions of the two metals, the surface of the movable mold-wall againstwhich the rst body is cast is covered or coated with a material whichwill prevent any elemental change of the metal of the first body or willrecouvert the portions of the iirst body elementally changed.

In the method described in the application referred to both bodies ofmetal are cast on opposite sides of a movable partition, which isgradually withdrawn as the casting proceeds. In the practice of thismethod it is preferred that the exposed surfaces of the partition shouldbe formed of a material which will prevent elemental change in themetals cast or will recouvert any elementallychanged metal. By either ofthese methods two qualities or grades of metal, as high and low carbonsteel, are brought together under such conditions that while certainportions of each grade will be unchanged, or practically so, there willbe an interchange of qualities from one to the other such as to resultin a gradual merging from the high carbon of one to the low carbon ofthe other and without any definable or ascertainable line of cleavage ordemarcation between the strata or layers.

o The gradual or decremental change from one o casting.

body or quality to the other is clearly shown in the cross-sections ofingots as actually *made The lines a b represent approximately thethickness of the stratum or layer forming the high-carbon body, and thelines b c in Fig. 1 or b b in Fig. 2 represent approximately thethickness of the stratum or layer forming the soft-metal body as thesebodies or strata were proportioned in that As the exterior walls of theingot became rapidly solidified and as it is desirable that the surfacesshould be unchanged, Ifound that in the particular case here illustratedthe interchange or interdiusion of the properties of the two qualitiesof steel thus employed existed substantially between the points andy-that is to say, in consequence of the interdiiusion referred to thesteel gradually changes or becomes reduced in carbonization from thepoints x to the points of lowest carbon, which iu Fig. 2 would be thecenter of the ingot, as at y, but in Fig. l would be at one side of theingot,- and this I have found to be the case generally throughout thecompound ingot-that is,

through other planes or sections; butin thus illustrating the peculiarfeatures of the present invention I do not wish to limit myself to anyspecific depth or extent of interdiffusive action, provided only a hardouter surface or wall is preserved of the desired thickness and from theinside of such wall there shall be a gradual and progressive change inthe carbonization such as to exclude the presence of any well-dened lineor plane of demarcation or cleavage, and such an ingot, for the purposesof the present invention, I would term a decrementally-carbonzed ingot.

I claim herein as my inventionl. A homogeneous cast ingot, having at theend of the casting operation asubstantial portion or layer of one kindor grade of metal, another substantial portion or layer of a differentkind orgrade of metal, and a substantial portion or layer intermediateof the others wherein the characteristics of the two metals mergegradually and equally into each other, said portions or layers beingparallel or approximately parallel to each other, substantially as setforth.

2. A homogeneous cast ingot, having at the end of the casting operation,a substantial portion formed of a steel of a certain carbonization,another substantial portion or layer formed of a steel having adifferent degree of carbonization and a portion intermediate of theother portions wherein the carbonization changes gradually ordecrementally and with substantial regularity from one layer to theother, said portions or layers being parallel or approximately parallelto each other, substantially as set forth.

3. A homogeneous casting ingot having at the end of the castingoperation a substantial stratum or layer approximately uniform inthickness formed of steel of a certain carbonization, and anothersubstantial stratum or layer approximately uniform in thickness formedof steel having a different degree of carbonization, and a stratum orlayer intermediate of the other two, decrementallycarbonized from onestratum or layer to the other, substantially as set forth.

In testimony whereof I have hereunto set my hand.

SYLVESTER A. COSGRAVE. Witnesses:

DARWIN S. WoLCo'r'r, F. E. GAITHER.

